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1. Effect of Systematic Uncertainties on Density and Temperature Estimates in Coronae of Capella

Author

Yu, Xixi, Kashyap, Vinay L., Del Zanna, Giulio, van Dyk, David A., Stenning, David C., Ballance, Connor P., and Warren, Harry P.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Statistics - Methodology
Abstract

We estimate the coronal density of Capella using the O VII and Fe XVII line systems in the soft X-ray regime that have been observed over the course of the Chandra mission. Our analysis combines measures of error due to uncertainty in the underlying atomic data with statistical errors in the Chandra data to derive meaningful overall uncertainties on the plasma density of the coronae of Capella. We consider two Bayesian frameworks. First, the so-called pragmatic-Bayesian approach considers the atomic data and their uncertainties as fully specified and uncorrectable. The fully-Bayesian approach, on the other hand, allows the observed spectral data to update the atomic data and their uncertainties, thereby reducing the overall errors on the inferred parameters. To incorporate atomic data uncertainties, we obtain a set of atomic data replicates, the distribution of which captures their uncertainty. A principal component analysis of these replicates allows us to represent the atomic uncertainty with a lower-dimensional multivariate Gaussian distribution. A $t$-distribution approximation of the uncertainties of a subset of plasma parameters including a priori temperature information, obtained from the temperature-sensitive-only Fe XVII spectral line analysis, is carried forward into the density- and temperature-sensitive O VII spectral line analysis. Markov Chain Monte Carlo based model fitting is implemented including Multi-step Monte Carlo Gibbs Sampler and Hamiltonian Monte Carlo. Our analysis recovers an isothermally approximated coronal plasma temperature of $\approx$5 MK and a coronal plasma density of $\approx$10$^{10}$ cm$^{-3}$, with uncertainties of 0.1 and 0.2 dex respectively.

Published
2024

6. Multistage analysis in astrostatistics

Author

Yu, Xixi, van Dyk, David, and Cohen, Edward

Abstract

A sequence of statistical analyses often needs to be conducted by different groups of researchers where the output of each analysis feeds into subsequent analyses. The statistical and systematic uncertainties of estimated quantities, especially high dimensional quantities, are hard to quantify and difficult to carry forward into subsequent analyses. In practice, uncertainty is often ignored and the estimated quantities are often treated as fixed and known, leading to erroneous interpretation of the data and underestimation of uncertainties. An astrophysical example occurs when we use the spectra of the solar and stellar coronae to estimate its density, temperature, and other composition. This requires the use of the results of atomic physical experiments and calculations. In the example, the interaction of statistical and atomic uncertainties in the context of a spectral model inform the analysis of the images of solar and stellar physics. The interpretation of the spectral observations in relation to atomic data and their statistical uncertainties is necessary for deriving meaningful uncertainties on the solar and stellar coronal plasma parameters like electron density and temperature. Understanding how uncertainties in the underlying atomic physics propagates to the uncertainties in the inferred plasma parameters is an essential component of this analysis. We propose a principled multistage analysis to carry forward the model-generated atomic data uncertainties and statistical uncertainties obtained from preliminary analyses to a primary analysis based on the observed spectral lines under a Bayesian framework. Besides the Bayesian methodology that considers the atomic data uncertainties as fully specified and uncorrectable (the so-called pragmatic Bayesian method), we allow for the ob- served data to update the atomic data uncertainties (the fully Bayesian method). The former generally increases the uncertainties on the inferred parameters compared with models that incorporate only statistical uncertainties. In contrast, the latter reduces the uncertainties on the inferred parameters. To incorporate uncertainties into a primary analysis, we summarize a Monte Carlo sample of the atomic data that represents its statistical uncertainty by treating these samples as equally likely. We also consider a degenerated multivariate Gaussian model derived via a principal component analysis as a low dimensional summary of the uncertainty in the atomic data. Markov Chain Monte Carlo based model fitting is implemented including Multi-step Monte Carlo Gibbs Sampler and Hamiltonian Monte Carlo. The multistage analysis is able to cope with case studies of different levels of complexity. Two-stage analysis is used to infer the plasma parameters in spectral analysis with case studies on the density-sensitive only Fe XIII lines and the temperature-sensitive only Fe XVII lines. Three-stage analysis is used on the density- and temperature-sensitive O VII lines in the X-ray regime considering one more parameter and its corresponding source of statistical uncertainties. This principled multistage analysis has the potential to be applied on complicated models with a variety of sources of uncertainties.

Published
2021
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11. Incorporating Uncertainties in Atomic Data Into the Analysis of Solar and Stellar Observations: A Case Study in Fe XIII

Author

Yu, Xixi, Del Zanna, Giulio, Stenning, David C., Cisewski-Kehe, Jessi, Kashyap, Vinay L., Stein, Nathan, van Dyk, David A., Warren, Harry P., and Weber, Mark A.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Information about the physical properties of astrophysical objects cannot be measured directly but is inferred by interpreting spectroscopic observations in the context of atomic physics calculations. Ratios of emission lines, for example, can be used to infer the electron density of the emitting plasma. Similarly, the relative intensities of emission lines formed over a wide range of temperatures yield information on the temperature structure. A critical component of this analysis is understanding how uncertainties in the underlying atomic physics propagates to the uncertainties in the inferred plasma parameters. At present, however, atomic physics databases do not include uncertainties on the atomic parameters and there is no established methodology for using them even if they did. In this paper we develop simple models for the uncertainties in the collision strengths and decay rates for Fe XIII and apply them to the interpretation of density sensitive lines observed with the EUV Imagining spectrometer (EIS) on Hinode. We incorporate these uncertainties in a Bayesian framework. We consider both a pragmatic Bayesian method where the atomic physics information is unaffected by the observed data, and a fully Bayesian method where the data can be used to probe the physics. The former generally increases the uncertainty in the inferred density by about a factor of 5 compared with models that incorporate only statistical uncertainties. The latter reduces the uncertainties on the inferred densities, but identifies areas of possible systematic problems with either the atomic physics or the observed intensities., Comment: in press at ApJ

Published
2018
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15. Electrophotocatalytic Tellurosulfonylation of Alkynes for the Synthesis of β-(Telluro)vinyl Sulfones

Author

Zhao, Zhiheng, Zhang, Huiping, Yan, Hongyan, Yu, Xixi, Gu, Lijun, and Zhang, Shengyong

Abstract

Difunctionalization of alkynes has gained a lot of interest in current organic chemistry. Herein, we developed an electrophotocatalytic multicomponent cascade reaction of alkynes and indoles with sulfinic acid sodium salts using elemental tellurium as the tellurium source. Using synergistic anodic oxidation and visible-light irradiation, various β-(telluro)vinyl sulfones have been prepared. This strategy features mild reaction conditions, excellent substrate scope, readily available starting materials, and great functional group tolerance.

Published
2024
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21. Effect of Kamistad gel on oral ulcer healing and TNF ⁃ α, IL ⁃ 6 and EGF expression in ulcer tissue of rat

Author

WANG Yiheng, WU Yingtao, YU Xixi, LI Lulu, DENG Songsong, LIU Mengjia, and WANG Wanchun

Subjects
Oral ulcer, Kamistad gel, Rat, Tumor necrosis factor⁃α, Interleukin⁃6, Epidermal growth factor, Medicine
Abstract

Objective To investigate the effect of Kamistad gel on oral ulcer healing and the expression of tumor necrosis factor α (TNF⁃α), interleukin 6 (IL⁃6) and epidermal growth factor (EGF) after oral administration in ulcer tis⁃ sue of rats and to provide animal experimental data for the clinical application of Kamistad gel. Methods The oral ul⁃ cer rat model was established by chemical cauterization. The rats were randomly divided into four groups: Kamistad group (Kamistad gel), befuxin group (befuxin gel), lidocaine group (lidocaine cream), blank control group (normal sa⁃ line), with 12 rats in each group. The ulcer area of the rats in each group was measured before and 1, 3 and 5 days after treatment; at 1 day after treatment, the duration of swabbing behavior within 3 minutes of intraoral capsaicin infusion was recorded to evaluate the degree of pain; the ulcer tissue was collected at 5 days after treatment, and the histopatho⁃ logical changes were observed by HE staining, the expression of TNF⁃α, IL⁃6 and EGF in the ulcer tissue was detected by immunohistochemistry and ELISA. Results At 1 day after treatment, the duration of mouth wiping induced by cap⁃ saicin was significantly shorter in the Kamistad group than in the blank control and befuxin groups (P < 0.05), but there was no significant difference between the Kamistad and lidocaine groups (P >0.05). At 5 days after treatment, the ulcer area was significantly smaller in the Kamistad group than in the blank control and lidocaine groups (P < 0.05), and there was no significant difference between the Kamistad and befuxin groups (P >0.05). At 5 days after treatment, H&E staining of the oral ulcer tissue sections showed significantly reduced levels of inflammatory cells and significantly pro⁃ liferated fibroblasts and better epithelial hyperplasia in the Kamistad group compared with those in the lidocaine and blank control groups, and there were no differences between the Kamistad and befuxin groups. At 5 days after treat⁃ ment, the expression levels of TNF⁃α, IL⁃6 and EGF in the ulcer tissue of rats in each group were significantly different (P < 0.05). Compared with the blank control and lidocaine groups, the expression of TNF⁃ α and IL⁃6 was significantly decreased and the expression of EGF was significantly increased in the Kamistad group (P < 0.05); there were no signifi⁃ cant differences in the expression of the above three factors between the Kamistad and befuxin groups (P > 0.05). Con⁃ clusion Kamistad gel exhibited anti⁃inflammatory, analgesic and healing effects on experimental oral ulcers.

Published
2019
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22. Research progress on primary burning mouth syndrome

Author

YU Xixi, WANG Caixia, and WANG Wanchun

Subjects
Burning mouth syndrome, Clinical manifestations, Pathogenesis, Diagnosis, Treatment, Medicine
Abstract

The pathogenesis of burning mouth syndrome (BMS) is not clear. Most scholars believe that primary BMS is a chronic neurological disease. Advanced diagnostic methods such as quantitative sensory testing (QST), trigeminal neuron electrophysiological recording and peripheral nerve blockade, structural analysis of epidermal nerve fiber densi⁃ ty (ENFD), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) classify neuropathic pain in most BMS patients as peripheral or central. Hormone replacement, dopaminergic drugs and noninvasive neuro⁃ modulation may be new approaches to BMS based on its pathogenesis. This article reviews the clinical features, patho⁃ physiological mechanism, new diagnostic methods and treatment of primary BMS and provides new ideas for the clinical diagnosis and treatment of BMS.

Published
2018
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23. The effects of intramuscular injections of vitamin B1 and B12 on pain, salivary components and taste in pa⁃ tients with burning mouth syndrome

Author

YU Xixi, Lü Jian, WANG Caixia, WANG Yiheng, DENG Songsong, LI Lulu, and WANG Wanchun

Subjects
Burning mouth syndrome, Saliva flow rate, Saliva components, Tast, Vitamin B1, Vitamin B12, Medicine
Abstract

Objective To determine differences in pain, salivary components and taste between burning mouth syn⁃ drome (BMS) patients and the normal population and to study the effects of intramuscular injections of vitamin B1 (VitB1) and vitamin B12 (VitB12) on BMS. Methods Before treatment: We observed and compared differences in un⁃ stimulated salivary flow rate (USFR); stimulated salivary flow rate (SSFR); salivary amylase, cortisol, and secretory im⁃ munoglobulin A (SIgA) concentrations; and taste levels between BMS patients and normal controls. After treatment: The treatment group received an intramuscular injection of 100 mg VitB1 and 0.5 mg VitB12 in the buttocks once per day for 10 days. The above indexes were recorded before and after treatment and compared. A visual analog scale (VAS) score was used to assess the degree of pain relief in patients and as a clinical evaluation index. Results Before treat⁃ ment: SSFR, salivary amylase levels and bitter taste levels of the treatment group were significantly lower than those of the control group (P < 0.05). The concentration of SIgA was significantly higher than that of the control group (P < 0.05), and the USFR and the cortisol concentration were not significant different from the those of the control group (P > 0.05). After treatment: The total effective rate of VitB1 and VitB12 on BMS was up to 70%. USFR was increased signifi⁃ cantly after treatment (P < 0.05), and the concentration of SIgA decreased (P < 0.05). There were no significant differ⁃ ences in the SSFR or the cortisol and salivary amylase concentrations (P > 0.05). Taste levels improved by varying de⁃ grees. Conclusions The abnormal decreases in SSFR, salivary amylase levels, and taste sensitivity and the abnormal increase in SIgA levels seen in BMS patients may be sensitive salivary indicators for the diagnosis of BMS. A VitB1 and VitB12 intramuscular injection is an effective treatment for patients with BMS, who showed pain relief. Changes in SIgA levels may be used as an indicator during follow⁃up and for the prognosis of BMS patients.

Published
2018
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38. Atomic Visualization of the 3D Charge Density Wave Stacking in 1T-TaS2by Cryogenic Transmission Electron Microscopy

Author

Wang, Gang, Yu, Xixi, Zhao, Erding, Li, Daiyue, Wang, Le, and Lin, Junhao

Abstract

Charge density waves (CDWs) in 1T-TaS2maintain 2D ordering by forming periodic in-plane star-of-David (SOD) patterns, while they also intertwined with orbital order in the caxis. Recent theoretical calculations and surface measurements have explored 3D CDW configurations, but interlayer intertwining of a 2D CDW order remains elusive. Here, we investigate the in- and out-of-plane ordering of the commensurate CDW superstructure in a 1T-TaS2thin flake in real space, using aberration-corrected cryogenic transmission electronic microscopy (cryo-TEM) in low-dose mode, far below the threshold dose for an electron-induced CDW phase transition. By scrutinizing the phase intensity variation of modulated Ta atoms, we visualize the penetrative 3D CDW stacking structure, revealing an intertwining multidomain structure with three types of vertical CDW stacking configurations. Our results provide microstructural evidence for the coexistence of local Mott insulation and metal phases and offer a paradigm for studying the CDW structure and correlation order in condensed-matter physics using cryo-TEM.

Published
2023
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49. Multistage analysis in astrostatistics

Author

Yu, Xixi, van Dyk, David, Cohen, Edward, Imperial College London, European Commission, and European Space Agency

Abstract

A sequence of statistical analyses often needs to be conducted by different groups of researchers where the output of each analysis feeds into subsequent analyses. The statistical and systematic uncertainties of estimated quantities, especially high dimensional quantities, are hard to quantify and difficult to carry forward into subsequent analyses. In practice, uncertainty is often ignored and the estimated quantities are often treated as fixed and known, leading to erroneous interpretation of the data and underestimation of uncertainties. An astrophysical example occurs when we use the spectra of the solar and stellar coronae to estimate its density, temperature, and other composition. This requires the use of the results of atomic physical experiments and calculations. In the example, the interaction of statistical and atomic uncertainties in the context of a spectral model inform the analysis of the images of solar and stellar physics. The interpretation of the spectral observations in relation to atomic data and their statistical uncertainties is necessary for deriving meaningful uncertainties on the solar and stellar coronal plasma parameters like electron density and temperature. Understanding how uncertainties in the underlying atomic physics propagates to the uncertainties in the inferred plasma parameters is an essential component of this analysis. We propose a principled multistage analysis to carry forward the model-generated atomic data uncertainties and statistical uncertainties obtained from preliminary analyses to a primary analysis based on the observed spectral lines under a Bayesian framework. Besides the Bayesian methodology that considers the atomic data uncertainties as fully specified and uncorrectable (the so-called pragmatic Bayesian method), we allow for the ob- served data to update the atomic data uncertainties (the fully Bayesian method). The former generally increases the uncertainties on the inferred parameters compared with models that incorporate only statistical uncertainties. In contrast, the latter reduces the uncertainties on the inferred parameters. To incorporate uncertainties into a primary analysis, we summarize a Monte Carlo sample of the atomic data that represents its statistical uncertainty by treating these samples as equally likely. We also consider a degenerated multivariate Gaussian model derived via a principal component analysis as a low dimensional summary of the uncertainty in the atomic data. Markov Chain Monte Carlo based model fitting is implemented including Multi-step Monte Carlo Gibbs Sampler and Hamiltonian Monte Carlo. The multistage analysis is able to cope with case studies of different levels of complexity. Two-stage analysis is used to infer the plasma parameters in spectral analysis with case studies on the density-sensitive only Fe XIII lines and the temperature-sensitive only Fe XVII lines. Three-stage analysis is used on the density- and temperature-sensitive O VII lines in the X-ray regime considering one more parameter and its corresponding source of statistical uncertainties. This principled multistage analysis has the potential to be applied on complicated models with a variety of sources of uncertainties. Open Access

Published
2020
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